Simplified Cook-Torrance

I have tried to make a fast pbr shader using simplified cook-torrance but it still seems slow, Was wondering if anyone knows if there is a faster way?

Code (CSharp):

1. Shader "Custom/simple AO " {
2.     Properties {
3.        
4.         _MainTex ("Base (RGB) Rough (A)", 2D) = "grey" {}
5.    
6.      
7.         _BumpMap ("Normalmap", 2D) = "bump" {}
8.      
9.      
10.  
11.  
12.  
13.     }
14.     SubShader {
15.         Tags { "RenderType"="Opaque" "LightMode"="ForwardBase" "IgnoreProjector"="True" }
16.         LOD 400
17.         CGPROGRAM
18.  
19.     #pragma surface surf Physical    exclude_path:prepass    novertexlights noforwardadd nolightmap halfasview
20.         sampler2D _MainTex;
21.  
22.         sampler2D _BumpMap;
23.    
24.  
25.  
26.      
27.      
28. struct Input {
29.         float2 uv_MainTex;
30.         half nv;
31.         float4 ambcolor;
32.      
33.      
34.         };
35.  
36.     inline    fixed4 LightingPhysical( SurfaceOutput s, half3 lightDir, half3 halfDir, half atten )
37.         {
38.      
39.     half diff=  max(0,dot(s.Normal,lightDir));
40.  
41.     half nh = saturate(dot (s.Normal, halfDir));
42.  
43.     half lh =  saturate(dot (halfDir,lightDir));
44.     half A=s.Alpha;
45.  
46.  
47.  
48.     half spec = ((A+1)*exp2(A*nh-A))/(1+(10*(lh*lh*lh)));
49.  
50.     fixed3 main =(s.Albedo+spec) * _LightColor0.rgb* (diff *atten);
51.  
52.     fixed4 c;
53.  
54.     c.rgb =main;
55.     c.a = 0;
56.     return c;
57.         }
58.    
59.         void surf (Input IN, inout SurfaceOutput o) {
60.          
61.          
62.          
63.             fixed4 c = tex2D (_MainTex, IN.uv_MainTex);
64.          
65.             fixed3 main = c;
66.             o.Albedo = main;
67.      
68.             o.Alpha =1*exp2(8* (c.a)+1) ;
69.             o.Normal =UnpackNormal(tex2D(_BumpMap, IN.uv_MainTex));
70.          
71.  
72.          
73.         }
74.         ENDCG
75.     }
76.     FallBack "Mobile/Diffuse"
77. }